WO2024107569A1 - Capture directe à plusieurs étages de co2 provenant de l'air - Google Patents

Capture directe à plusieurs étages de co2 provenant de l'air Download PDF

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WO2024107569A1
WO2024107569A1 PCT/US2023/079045 US2023079045W WO2024107569A1 WO 2024107569 A1 WO2024107569 A1 WO 2024107569A1 US 2023079045 W US2023079045 W US 2023079045W WO 2024107569 A1 WO2024107569 A1 WO 2024107569A1
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sorbent
working fluid
vol
heated
exposing
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Bennett D. Marshall
Simon C. Weston
Aaron W. Peters
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ExxonMobil Technology and Engineering Company
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
    • B01D53/0407—Constructional details of adsorbing systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B01D53/06—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with moving adsorbents, e.g. rotating beds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
    • B01D53/0462—Temperature swing adsorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/20—Organic adsorbents
    • B01D2253/204—Metal organic frameworks (MOF's)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/25—Coated, impregnated or composite adsorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/30—Physical properties of adsorbents
    • B01D2253/34—Specific shapes
    • B01D2253/342—Monoliths
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2256/00—Main component in the product gas stream after treatment
    • B01D2256/10—Nitrogen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/50—Carbon oxides
    • B01D2257/504—Carbon dioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/06—Polluted air
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
    • B01D2259/40—Further details for adsorption processes and devices
    • B01D2259/40001—Methods relating to additional, e.g. intermediate, treatment of process gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
    • B01D2259/40—Further details for adsorption processes and devices
    • B01D2259/40011—Methods relating to the process cycle in pressure or temperature swing adsorption
    • B01D2259/40043—Purging
    • B01D2259/4005—Nature of purge gas
    • B01D2259/40052—Recycled product or process gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
    • B01D2259/40—Further details for adsorption processes and devices
    • B01D2259/40083—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption
    • B01D2259/40088—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption by heating
    • B01D2259/4009—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption by heating using hot gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
    • B01D2259/40—Further details for adsorption processes and devices
    • B01D2259/404—Further details for adsorption processes and devices using four beds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
    • B01D53/0407—Constructional details of adsorbing systems
    • B01D53/0438—Cooling or heating systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1431—Pretreatment by other processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1431—Pretreatment by other processes
    • B01D53/1437—Pretreatment by adsorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1456—Removing acid components
    • B01D53/1475—Removing carbon dioxide
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/40—Capture or disposal of greenhouse gases of CO2

Definitions

  • Capture and sequestration of CO2 can contribute to efforts for reducing or minimizing the amount of CO2 introduced into the atmosphere by various commercial, residential, and/or industrial processes.
  • One option is to attempt to capture CO2 as it is generated at various types of point sources.
  • Another option is to attempt to remove CO2 directly from air.
  • U.S. Patent Application Publication 2017/0113184 describes single stage methods for removing CO2 from air.
  • the methods include forming a recycle stream corresponding to a portion of the CCU-containing effluent from the removal process and mixing the recycle stream with the air input flow to the process.
  • the CCF-enriched air flow is the exposed to a sorbent. Mixing a recycle stream with the ambient air increases the concentration of CO2 in the input flow, but does not reduce the volume of gas that requires processing in the removal stage.
  • systems and methods are provided for performing direct air capture using a multi-stage separation system.
  • a method for separation of CO2 from an input flow stream includes: exposing a first gas flow containing 600 vppm or less of CO2 to at least one first contactor of a plurality of contactors to form a first CCE-depleted gas flow, the at least one first contactor comprising a first sorbent having selectivity for CO2 sorption supported on one or more first monoliths, the exposing the first gas flow further forming a first sorbent comprising sorbed CO2; exposing a second gas flow containing 600 vppm or less of CO2 to at least one second contactor of the plurality of contactors to form a second CCE-depleted gas flow, the at least one second contactor comprising a sorbent having selectivity for CO2 sorption supported on one or more monoliths, the exposing the second gas flow further forming a second sorbent comprising sorbed CO2; exposing the first sorbent comprising sorbed CO2 to a first
  • a system for separation of CO2 includes: a plurality of initial stage contactors comprising a sorbent having selectivity for sorption of CO2, each initial stage contactor having a sorption step inlet, a sorption step outlet, at least one additional inlet, and at least one additional outlet, the plurality of initial stage contactors corresponding to at least a first initial stage contactor and a final initial stage contactor; a second separation stage having a second separation stage inlet, a product outlet, and a recycle outlet; an initial stage effluent conduit providing fluid communication between the second separation stage inlet and the at least one additional outlet of the final initial stage contactor, the initial stage effluent conduit containing an effluent flow comprising 95 vol% or more of N2 and 1.0 vol% or more of CO2; a recycle conduit providing fluid communication between the recycle outlet and the at least one additional inlet of the first initial stage contactor, the recycle conduit containing a recycle gas containing 95 vol% or more of N2
  • FIG. 1 shows an example of a sorption step in an initial separation stage.
  • FIG. 2 shows an example of a process flow loop for integrating the desorption and cooling steps of an initial separation stage with a second separation stage.
  • FIG. 3 shows another example of a process flow loop for integrating the desorption and cooling steps of an initial separation stage with a second separation stage.
  • FIG. 4 shows an example of a flow channel of a parallel flow channel monolith.
  • FIG. 5 shows a representation of a large plurality of contactors in various process steps in an initial separation stage.
  • FIG. 6 shows an example of using a rotary wheel as a sorbent bed for an initial separation stage.
  • FIG. 7 shows an example of integration of two rotary wheels as sorbent beds in an initial separation stage.
  • FIG. 8 shows CO2 adsorption versus CO2 partial pressure for an amine-appended metal organic framework material.
  • systems and methods are provided for using a multi-stage capture process for capture of CO2 from air.
  • a multi-stage sorption process is used instead of attempting to directly produce a high purity CO2 stream from CO2 desorbed from air.
  • a first or initial sorption process is used to sorb CO2 from air.
  • the desorption step of the initial stage is used to form a secondary CCL-containing stream (corresponding to an initial stage effluent) that is passed into one or more additional sorption stages.
  • This secondary CO2- containing stream can be at a concentration of roughly 1.0 vol% or more.
  • Sorption of CO2 from the secondary CCL-containing stream is performed using a different contacting method, such as a contacting method that is higher efficiency, but that would have an unreasonably high cost of operation at the higher gas volumes required for one-step capture of CO2 from air.
  • a different contacting method such as a contacting method that is higher efficiency, but that would have an unreasonably high cost of operation at the higher gas volumes required for one-step capture of CO2 from air.
  • the initial CO2 sorption stage can be focused on reducing costs associated with dilute capture, while the second (or later) CO2 sorption stage can focus on reducing costs associated with producing a CCL-containing output stream with a CO2 concentration of 80 vol% or more, or 90 vol% or more, or 95 vol% or more, such as up to being a substantially pure CCE-containing output stream.
  • This high purity output stream can then be sequestered and/or used for further processing in any convenient manner.
  • the transfer of heat from the first stage desorption step to the first stage sorption step can be improved, providing further reduction in operating cost.
  • amine scrubbing is the industry standard technology for CO2 capture at higher CO2 partial pressures.
  • amine scrubbing would require an unfeasibly large footprint and capital expenditure. This is because the energy cost / equipment footprint / capital expenditure for amine scrubbing scales with the volume of gas that is passed through the amine scrubbing system.
  • sold amine adsorbents using structured contactors are currently the preferred means of amine based direct air capture.
  • the first set of challenges is related to the goal of producing an output flow corresponding to a CCh-containing stream with a CO2 content of 80 vol% or more, or 90 vol% or more, such as up to being substantially entirely composed of CO2.
  • This type of output stream is required to allow for either further processing / use of the CC -containing output flow, or to allow for efficient sequestration I storage of the CCh-containing output flow.
  • achieving this type of high purity CO2 stream as an output flow constrains the options for performing the desorption cycle.
  • the second set of challenges is related to the dilute nature of air as a COi-containing stream. Due to the low concentration of CO2, the solid sorbent needs to have a high enthalpy of sorption. This assists with driving sorption of the CO2 in spite of the dilute nature of the stream. However, such a high enthalpy of sorption means that a similar amount of energy input is needed to facilitate desorption during the desorption step of the process cycle. This results in the energy management challenge when attempting to produce a high purity CO2 stream.
  • the multi-stage system allows the separate challenges involved in direct air capture to be handled in a substantially separate manner.
  • an initial stage can be used that has relatively low capital and/or processing costs per unit volume of air that is processed, so that the large volume of sorbent needed for sorbing CO2 from air is not multiplied by the higher capital / energy usage / other operating costs associated with forming a high purity CO2 stream.
  • the initial separation stage is used to form a first stage effluent with a CO2 concentration of roughly 1.0 vol% or more.
  • This type of first stage effluent can be formed using a method that has substantially reduced capital costs and/or energy intensity per volume of CO2 and/or per volume of air processed. For example, by only achieving a CO2 concentration of 1.0 vol% to 5.0 vol%, use of reduced pressures (i.e., vacuum) can be avoided. Thus, all of the additional equipment footprint associated with performing a vacuum desorption process is not required, resulting in substantial capital cost savings. Energy savings are also achieved by avoiding the need to operate the pumps typically associated with a vacuum desorption process.
  • the first stage effluent can then be passed into a second separation stage for separating the first stage effluent to form a high purity CC -containing stream.
  • the input gas flow volumes and/or contactor volumes associated with the second separation stage are substantially smaller than the input air flow volumes / contactor volumes associated with the first stage. This can allow a separation process with a higher capital costs I processing costs per volume to be used in the second stage, as the flow volumes / contactor volumes associated with the second stage will be substantially lower.
  • the flow volumes and/or contactor volumes associated with the second stage can be smaller than the flow volumes and/or contactor volumes associated with the first stage by a factor of 20 or more, or 25 or more, or 50 or more, or 100 or more, such as up to a factor of 250 or possibly still higher.
  • an amine tower is an example of a separation process that can produce a CCh-containing stream with a purity of 90 vol% or more, or 95 vol% or more, such as up to 99 vol% or possibly still higher.
  • the volume of amine tower required to process a CO -containing input flow is primarily driven by hydraulic considerations (e.g., the volume flow rate of the input flow).
  • Using a first stage to convert air containing roughly 400 vppm of CO2 into a first stage effluent containing roughly 10,000 vppm of CO2 means that the size of the amine tower used to capture the CO2 from the first stage effluent can be smaller than the size of the corresponding amine tower to directly capture the CO2 from air by a factor of 25. As a practical matter, this would mean using only 1 amine tower instead of 25 amine towers to process a given amount of CO2.
  • the sorption / desorption cycle is managed using a working fluid that includes a substantial amount of nitrogen.
  • nitrogen is the primary component of air.
  • using nitrogen as a working fluid would result in adding back in the same diluent that the separation process is designed to remove.
  • conventional direct air capture processes use steam as a working fluid, so that a simplified method (condensation) is available for removing the steam from the high purity CO2- containing product.
  • the CO2 concentration in the first stage effluent is between 1.0 vol% to 5.0 vol%, or 1.0 vol% to 3.5 vol%, or 1.0 vol% to 2.0 vol%, or 1.5 vol% to 5.0 vol%, or 1.5 vol% to 3.5 vol%, or 2.0 vol% to 5.0 vol%, or 2.0 vol% to 3.5 vol%.
  • the output flow from the initial stage already has a substantial diluent content, so that the presence of nitrogen in the working fluid is not detrimental.
  • the use of steam in the initial desorption stage can be reduced, minimized, or eliminated. This avoids the substantial costs associated with using steam to heat and/or desorb CO2 from the large sorbent volumes associated with the initial separation stage.
  • the separation in the initial separation stage can be performed while maintaining a pressure in the initial separation stage of 90 kPa-a or more, or 95 kPa-a or more, or 100 kPa-a or more.
  • vacuum-assisted desorption is not performed.
  • the initial stage avoids the use of steam as a desorption fluid, as well as avoiding the need to generate pressures below 90 kPa-a during desorption. Due to the large contactor volumes involved in processing air for CO2 capture on a commercial scale, avoiding the use of steam and/or sub-ambient pressures provides a substantia] cost savings.
  • the cost reduction in the initial stage may be partially offset by operating the initial stage at a pressure greater than 110 kPa-a.
  • the working fluid in the initial separation stage also contains 0.08 vol% to 0.5 vol% of CO2 even prior to being used for desorption of CO2 from a sorbent bed.
  • addition of CO2 to a working fluid would be viewed as a disadvantage, as this would likely mean that previously separated CO2 was being recycled and mixed with a lower concentration input flow.
  • the working fluid can be generated as a by-product or side stream from the second separation stage. For example, when the second separation stage corresponds to a steam and vacuum-assisted sorption / desorption cycle with a solid sorbent, the sorption I desorption cycle will generally produce a secondary effluent with a relatively low content of CO2.
  • This secondary effluent can be used as at least a portion of the working fluid.
  • the initial separation stage generates a CCh-containing effluent having a substantially smaller volumetric flow than the air input flow for the initial separation stage.
  • the initial stage effluent has a CO2 concentration of 1.0 vol% or more, or 1.5 vol% or more, or 2.0 vol% or more, such as up to 5.0 vol% or possibly still higher.
  • the CO2 content of the input flow to the initial stage will typically be 500 vppm or less (such as the roughly 400 vppm present in air).
  • the volume of initial stage effluent is lower than the volume of the input flow to the initial stage by at least a factor of 20.
  • the reduction in flow volume corresponds to at least a factor of 25.
  • This reduction in volume flow to the second separation stage provides substantial reductions in the energy consumed and/or other processing costs for production of a high purity COz-containing output flow.
  • the second separation stage can correspond to an amine scrubber and/or another type of separator where the volume and energy costs scale proportionally with the volume of the input gas flow to the separation stage.
  • using the initial separation stage to form an initial stage effluent where the volume is reduced by a factor of 20 or more, or 25 or more, (such as up to 100 or possibly still more) provides a corresponding decrease in the size and associated energy costs for operating the stage.
  • the second separation stage can correspond to a separation based on using a solid sorbent, such as a temperature swing and vacuum-assisted solid sorbent separation stage.
  • a solid sorbent such as a temperature swing and vacuum-assisted solid sorbent separation stage.
  • reducing the volume of input flow to the second separation stage allows for a reduction in the volume I mass of sorbent that is required to perform the separation, with a corresponding reduction in energy costs for performing the separation. Because the processing costs with the second (and/or subsequent) separation stage are reduced dramatically, the combination of the processing costs for the initial separation stage and the second separation stage can still be below the processing costs for a single separation stage.
  • Still further reductions in volume / mass for the sorbent in the second stage can be achieved by operating the process loop corresponding to the initial stage desorption step, initial stage cooling step, and second separation stage at pressures greater than 110 kPa-a.
  • at least a portion (such as up to substantially all) of the input flow to the second separation stage corresponds to at least a portion of the desorption effluent from the first or initial separation stage. If the initial stage effluent is at a pressure greater than 110 kPa-a, the volume of the initial stage effluent is further reduced, resulting in further reductions in the volume of the input flow to the second separation stage.
  • pressurizing the input flow to the second separation stage provides a corresponding proportional increase in the partial pressure of CO2 in the input flow. This can be beneficial for increasing the throughput in the second separation stage, which can then allow for further increases in the number of first stage contactors that can be paired with a given volume for the second separation stage.
  • operating with a pressurized working fluid can increase the operating cost of the overall system (first separation stage plus second separation stage).
  • capital costs for equipment plus the required equipment footprint can be reduced when using a pressurized working fluid.
  • selecting operation with a working fluid at near ambient pressure versus a working fluid at pressures greater than 110 kPa-a can depend on trade-offs between which type of benefit is more valuable (reduced operating cost versus reduced capital cost I equipment footprint).
  • Using a nitrogen-based working fluid can provide still other benefits. For example, for sorbents (such as amine-based sorbents) that can potentially degrade in the presence of oxygen at elevated temperatures, using a nitrogen-based working fluid can avoid the need to make trade-offs between heating or cooling the sorbent due to concern about the presence of oxygen in the sorbent environment. In conventional systems, such trade-offs occur because steam is used as the primary purge and temperature control fluid. By reducing, minimizing, or avoiding the use of steam, concerns about condensation of water can also be reduced while allowing for more flexibility in recovering heat to minimize energy costs.
  • a sorption / desorption cycle for sorption of CO2 by a solid sorbent can typically include at least three steps.
  • a first step in the process cycle corresponds to an adsorption step, where the loading of CO2 on the sorbent is increased by exposing the sorbent to CCF-containing input flow under sorption conditions. This also generates an exhaust stream that is depleted in CO2 relative to the input flow.
  • the input flow can include a substantial portion of air, such as being composed entirely of air.
  • the input flow can include a substantial portion of an effluent from the initial separation stage, such as being composed entirely of an effluent from the initial separation stage.
  • a second step in the process is a desorption step.
  • the desorption step generates an effluent that is enriched in CO2 relative to the input flow to the sorbent environment.
  • the third step in the process is a step to return the sorbent / sorbent environment to the conditions for performing the next sorption step.
  • amine-based solid sorbents typically need to be cooled after desorption and prior to exposure to the input flow.
  • the goal of the initial sorption stage can be to generate an initial stage output flow (i.e., an initial stage effluent) having a CO2 concentration of 1.0 vol% or more, or 1.5 vol% or more, or 2.0 vol% or more, such as up to 5.0 vol% or possibly still higher. At least a portion of this initial stage effluent can then be passed into a second sorption / desorption stage. The second separation stage (and/or optional further additional separation stages) is then used to separate the initial stage effluent to form at least a high purity CCh-containing stream and stream corresponding to at least a portion of the working fluid.
  • FIG. 1 and FIG. 2 show an example of a process flow for implementing a two-stage CO2 capture process.
  • FIG. 1 shows an example of the CO2 sorption step in the initial stage of the two-stage CO2 separation process.
  • a large plurality of sorbent beds are exposed to a flow of air (and/or another fluid having a CO2 concentration of 600 vppm or less, or 500 vppm or less, or 400 vppm or less, such as down to 100 vppm or possibly still lower.
  • FIG. 1 and FIG. 2 show an example of a process flow for implementing a two-stage CO2 capture process.
  • FIG. 1 shows an example of the CO2 sorption step in the initial stage of the two-stage CO2 separation process.
  • a large plurality of sorbent beds are exposed to a flow of air (and/or another fluid having a CO2 concentration of 600 vppm or less, or 500 vppm or less, or 400 vppm or less, such as down to 100
  • any convenient number of sorbent beds can be exposed to air during a sorption process. Due to the relatively low concentration of CO2 in air, achieving a target loading of CO2 on a sorbent can take a relatively long time.
  • the target loading can correspond to an equilibrium loading of CO2 at the sorption temperature, a fraction of the equilibrium loading, a loading that is achieved after a fixed time, or another convenient target value.
  • a majority of the sorbent beds can perform the CO2 sorption step.
  • a smaller number of beds at any given time can perform the various desorption / regeneration processes that are needed to return a sorbent bed to a condition where it is ready to perform additional sorption of CO2. This can allow an increased amount of CO2 to be sorbed on a sorbent bed prior to desorbing CO2 to form the first stage effluent while still allowing the second stage of the separation process to operate in a substantially continuous manner.
  • FIG. 2 shows how the cooling and desorption steps of the initial separation stage are integrated with the second separation stage via use of a working fluid.
  • at least two sorbent beds are involved in the portion of the process flow that integrates the desorption and cooling steps with the second separation stage.
  • At least one sorbent bed 223 can be in the desorption step of the process cycle, while one or more sorbent beds 224 can be in the cooling step of the process cycle.
  • the cooling step comes after the desorption step in the process cycle.
  • the one or more sorbent beds 224 correspond to sorbent bed(s) that have already completed the desorption step of the process cycle.
  • a working fluid 235 is used to assist with managing the temperature of the at least one sorbent bed 223 and the temperature of the one or more sorbent beds 224.
  • the working fluid 235 can also act as a sweep gas for the at least one sorbent bed 223 that is in the desorption step of the sorption I desorption cycle.
  • working fluid 235 is at a relatively low temperature.
  • the temperature of working fluid 235 after leaving second separation stage 230 can be 40°C or less, or 30°C or less, such as down to 0°C or possibly still lower.
  • the working fluid 235 is first passed into the one or more sorbent beds 224 that are in the cooling step of the sorption / desorption cycle.
  • the one or more sorbent beds 224 can be at a temperature of 40°C to 200°C, or 100°C to 200°C, or 125°C to 200°C, or 40°C to 150°C, or 100°C to 150°C, or 40°C to 100°C. Exposing the working fluid 235 to the one or more sorbent beds 224 results in cooling of the one or more sorbent beds 224 while also forming a partially heated working fluid 245. The flow rate of working fluid 235 and length of the cooling step can be selected so that the one or more sorbent beds 224 are at or below a target temperature for starting the next sorption step in the process cycle.
  • the target temperature for starting a sorption step can be 130°C or less, 115°C or less, 100°C or less, or 85°C or less, or 70°C or less, or 55°C or less, such as down to 10°C or possibly still lower.
  • additional cooling can be achieved during the cooling step by recycling (not shown) at least a portion of the output flow from the one or more sorbent beds 224 (i.e., at least a portion of partially heated working fluid 245) back to the entry of the one or more sorbent beds 224.
  • the volume of gas available for cooling the one or more sorbent beds 224 can be increased without causing a corresponding increase in the total volume of gas in the overall working fluid loop.
  • the recycle loop for the one or more sorbent beds 224 can include a heat exchanger, to allow for cooling of the recycled gas flow.
  • the partially heated working fluid 245 can then be further heated 250 to form heated working fluid 255.
  • Heating 250 can be performed using any convenient method, such as heat exchange, electrical heating, or heating in a furnace. Heating 250 is used to increase the temperature of heated working fluid 255 to a target temperature for use in the desorption step. In various aspects, the heated working fluid can be heated to a target temperature of 100°C or more, or 125°C or more, or 150°C or more, or 170°C or more, such as up to 210°C or possibly still higher.
  • the heated working fluid 255 is then passed into the at least one sorbent bed 223 that is in the desorption step of the sorption I desorption cycle.
  • the heated working fluid 255 heats the at least one sorbent bed 223 to assist with desorption of sorbed CO2. This results in production of a first stage effluent 265.
  • the desorption of the sorbed CO2 is endothermic, so the first stage effluent 265 will be at a lower temperature than the temperature of the heated working fluid 255.
  • the temperature of the first stage effluent can be between 70°C to 200°C, or 100°C to 200°C, or 125°C to 200°C, or 70°C to 150°C, or 100°C to 150°C, or 70°C to 100°C.
  • heat can be effectively transferred from the one or more beds 224 that are in the cooling step to the at least one bed 223 that is in the desorption step. This reduces or minimizes the amount of energy required to achieve desorption of CO2 during the desorption step of the sorption / desorption cycle.
  • heating with a working fluid decreases the partial pressure of CO2 in the gas phase, allowing for a lower temperature of stream 255. This lower temperature is important for many solid amine adsorbents, where elevated temperatures can result in degradation.
  • the first stage effluent 265 is then passed into a second separation stage 230.
  • the second separation stage 230 can be any convenient type of separation stage for separating an input flow containing 1.0 vol% or more of CO2 to form a) a CO2 output flow 275 having a CO2 concentration of 80 vol% or more, or 90 vol% or more, and b) at least one additional output flow 272 (corresponding to at least a portion of the working fluid) that contains a majority of the nitrogen from first stage effluent 265.
  • Examples of separation methods that can form such a CO2 output flow when starting with an input flow containing 1.0 vol% or more of CO2 include, but are not limited to, a liquid amine scrubbing process or a single stage vacuum temperature swing adsorption process.
  • the additional output flow 272 can be formed from the remaining portion of the initial stage effluent.
  • the additional output flow 272 can have a CO2 content of 0.08 vol% to 0.5 vol%.
  • the additional output flow 272 also corresponds to a nitrogen-enriched gas flow, with an N2 content of 95 vol% or more, or 97 vol% or more, or 99 vol% or more, such as up to being composed substantially of only CO2 and N2.
  • a flow of make-up gas (such as make-up nitrogen 232) can be added to additional output flow 272 to maintain a desired volume of gas within the working fluid loop.
  • a purge flow (not shown) is also generated during the transition of a sorbent bed from an adsorption step to the cooling / desorption loop. At the end of an adsorption step, the void space within a sorbent bed is full of air with 21% oxygen.
  • nitrogen or another convenient purge gas can be passed through the sorbent bed prior to connecting the sorbent bed to the working fluid loop. For example, roughly 1 bed volume of nitrogen can be passed through the sorbent bed to push out the air prior to connecting the sorbent bed to the working fluid loop. The effluent from this mini-purge step is vented to the atmosphere.
  • FIG. 3 shows another example of a process flow for using a working fluid generated by the second separation stage as part of the cooling and desorption steps in the initial separation stage.
  • the overall process flow in FIG. 3 is similar to the process flow in FIG. 2.
  • the desorption output flow 365 contains roughly 1.0 vol% or more of CO2, or 1.5 vol% or more, or 2.0 vol% or more, such as up to 5.0 vol% or possibly still higher.
  • the desorption output flow 365 from the at least one sorbent bed 223 is not used as the first stage effluent. Instead, the desorption output flow 365 is passed through an additional heater 359 to form a heated desorption output flow 381.
  • the heated desorption output flow 381 is then used to pre-heat one or more additional sorbent beds 328 that are at the start of the desorption step.
  • the flow 385 exiting from the one or more additional sorbent beds 328 corresponds to an initial stage effluent that is then passed into second separation stage 230.
  • the process flow in FIG. 3 can be beneficial in situations where the target desorption temperature is higher than the temperature at the end of the sorption step by 20°C or more, or 30°C or more, or 40°C or more, such as up to 100°C or possibly still more.
  • heated desorption output flow 381 to pre-heat the one or more additional sorbent beds 328 allows a portion of the heating prior to desorption to be performed using a stream with a composition that matches the output flow from the desorption step. Because the stream is heated, sorption of CO2 on the sorbent substantially does not occur. Additionally, because the goal is pre-heating, the heated desorption output flow 381 can optionally be at a lower temperature than the heated working fluid 255. In various aspects, heated desorption output flow 365 can be heated to a temperature of 70°C to 200°C, or 70°C to 150°C, or 70°C to 100°C, or 100°C to 200°C, or 100°C to 150°C.
  • the one or more additional beds 328 can be at a temperature of 50°C to 125°C, or 50°C to 100°C, or 50°C to 85°C, or 70°C to 125°C, or 70°C to 100°C.
  • using the heated desorption output flow 381 to pre-heat the one or more additional sorbent beds 328 can allow the flow rate of working fluid to be reduced.
  • the total volume of gas needed to achieve a target temperature during the desorption step can be calculated based on the volume of sorbent. This volume of gas for achieving the target temperature during the desorption step is a constraint on the operation of the initial separation stage, and will often define the minimum required gas flow rate for the cooling and desorption step.
  • all of the heat provided for achieving the target desorption temperature is provided by heated working fluid 255.
  • a portion of the heat for achieving the target desorption temperature is provided by heated desorption output flow 381.
  • the volume of heated working fluid 255 can be reduced by an amount corresponding to the amount of heating provided by heated desorption output flow 381.
  • the flow rate of working fluid in FIG. 3 can be reduced relative to FIG. 2 while still achieving the same target desorption temperature. It is noted that the reduction in flow rate in FIG. 3 is limited by the fact that heated desorption output flow 381 includes substantially all of heated working fluid 255. Therefore, reducing the flow rate for heated working fluid 255 also reduced the flow rate for heated desorption output flow 381.
  • the configurations in FIG. 2 or FIG. 3 can also provide benefits when operating the process flow so that the initial separation stage effluent is passed into the second separation stage at a pressure of 110 kPa-a or higher.
  • the partial pressure of CO2 in the second stage is increased by a corresponding amount for a given concentration of CO2 in the first stage effluent.
  • increasing the partial pressure of CO2 in the input flow results in corresponding increase in sorption efficiency during a sorption / desorption cycle.
  • the initial separation stage effluent can be passed into the second separation stage at a pressure of 110 kPa-a or higher, or 150 kPa-a or higher, or 200 kPa-a or higher, or 300 kPa-a or higher, or 400 kPa-a or higher, such as up to 1000 kPa-a or possibly still higher.
  • the entire working fluid loop plus the second separation stage can be operated at elevated pressure in order to obtain the benefit of passing the initial separation stage effluent into the second separation stage at elevated pressure.
  • a compressor can be used to increase the pressure of initial stage effluent 265 (FIG. 2) or 385 (FIG. 3). More generally, any convenient method for providing the initial stage effluent at elevated pressure can be used.
  • the sorbent can correspond to a solid sorbent.
  • solid amine-based adsorbents are metal organic frameworks (MOF) which have amines bound to open metal sites along the axis of the MOF crystal.
  • MOF metal organic frameworks
  • Other examples include amines which have been impregnated in solid supports such as MOF crystals, mesoporous silica, and activated carbons.
  • Polymeric amines provide still another example of an amine-based solid sorbent.
  • any convenient type of solid sorbent amine-based or non-amine- based
  • non-amine-based sorbents can include, but are not limited to, polymeric sorbents, MOFs, activated carbons, and mesoporous silica.
  • the sorption step in direct air capture processes necessarily operates at pressures near 100 kPa-a, in order to minimize costs associated with pressurizing large volumes of air. Due to this desire to minimize energy costs for pressurizing the large volumes of air, there is little tolerance for pressure drop through the sorbent structure for the initial separation stage. For this reason, in various aspects, structured adsorbents are used which allow for the pressure drop during the sorption step to be reduced or minimized.
  • An example of this type of sorbent support structure is a parallel channel monolith.
  • FIG. 4 shows an example of a cross-sectional view of a channel in a monolith.
  • the sorbent layer 420 is coated on the interior walls of the channel of solid support 410.
  • the combination of solid support 410 and sorbent layer 420 define gas channel 430.
  • the monolith could be made entirely out of an active material, so that a separate sorbent layer is not coated on the interior walls.
  • a monolith can be formed from a mixture of an active material and binder, so that a separate sorbent layer is not required on the interior surfaces of the channels.
  • the solid monolith support can be formed from any convenient type of material. Stainless steel is an example of a reasonably low cost material that provides sufficient durability and structural support. In other aspects, monoliths can be formed from other materials, including (but not limited to) ceramics, metal oxides (such as alumina), or polymeric materials. Sorbents can be applied to monoliths via any convenient method, such as dip-coating or other methods for applying a washcoat to a monolith.
  • the sorbent layer contains adsorbent, binder and optionally macro voids.
  • the sorbent layer can have any convenient composition that provides a target level of sorption capacity when applied to a monolith support.
  • a sorbent layer can contain 60 vol% sorbent, 25 vol% binder and 15 vol% macro voids.
  • the sorbent content of a sorbent layer can range from 10 vol% to 90 vol% of the sorbent layer and 10 vol% to 90 vol% binder.
  • Macro voids are optional. When macro voids are present, 0.1 vol% to 50 vol% of the sorbent layer can correspond to the macro voids.
  • one option for characterizing the gas channels is based on specifying a number of cells per unit cross-sectional area (a cell density), in combination with specifying a percentage of the monolith cross-sectional area that corresponds to an open volume for passage of gas (i.e., cross-sectional area that is not part of the support material or the sorbent layer).
  • a monolith can be used that has a cell density of 50 cells per square inch (cpsi) to 2000 cpsi, or 100 cpsi to 1000 cpsi. This corresponds to roughly 8.0 cells / cm 2 to roughly 310 cells / cm 2 .
  • a monolith can have an open cross-sectional area of 25% to 80%.
  • the open cross-sectional area is defined based on a cross-section that is orthogonal to the average direction of gas flow within the monolith.
  • solid sorbents are one option for the sorbent material.
  • solid amine-based adsorbents are metal organic frameworks (MOF) which have amines bound to open metal sites along the axis of the MOF crystal.
  • MOF metal organic frameworks
  • Other examples include amines which have been impregnated in solid supports such as MOF crystals, mesoporous silica, and activated carbons.
  • Polymeric amines provide still another example of an amine-based solid sorbent.
  • any convenient type of solid sorbent (amine-based or non-amine- hased) can he used as a COr sorbent in a second separation stage.
  • non-amine-based sorbents can include, but are not limited to, polymeric sorbents, MOFs, activated carbons, and mesoporous silica.
  • the support structure for the solid sorbent can be any convenient type of support structure.
  • support structures for solid sorbents can include, but are not limited to, monoliths with sorbent supported on surfaces of the monolith; packed beds with sorbent supported on the particles used to form the packed beds; and/or porous substrates where the sorbent is supported in the pores and/or the sorbent forms part of the substrate. Because of the substantially lower gas volumes in the second separation stage, increasing the pressure of the input flows to the second separation stage to overcome pressure drops is substantially less costly from an energy standpoint. Thus, solid sorbent configurations that involve greater pressure drops, such as packed beds or porous substrates, can be used while still realizing substantial energy savings relative to conventional direct air capture configurations. Additionally or alternately, monoliths having the characteristics described for the sorbent support in the initial separation stage can be used.
  • the second separation stage is operated using a solid sorbent
  • conventional CO2 sorption and/or desorption conditions can be used for the sorption / desorption cycle.
  • the sorption and/or desorption conditions can vary depending on a variety of factors, including the nature of the sorbent material. For sorption, this can include exposing the solid sorbent to the first stage effluent at a temperature between 0°C and 100 °C, while desorption is performed at a temperature between 70°C and 170°C.
  • the desorption can be performed at pressures of 90 kPa-a or less, or 75 kPa- a or less, or 50 kPa-a or less, such as down to 1.0 kPa-a or possibly still lower.
  • the pressure during desorption can be lower than the pressure during sorption by 30 kPa or more, or 50 kPa or more, or 100 kPa or more, such as up to 1.0 MPa or possibly still more.
  • the pressure during desorption can be 80 kPa-a to 120 kPa-a, or 90 kPa- a to 120 kPa-a, or 80 kPa-a to 110 kPa-a, or 90 kPa-a to 110 kPa-a.
  • Another option for a second separation stage can be to use a liquid-based amine system for CO2 removal, such as a conventional amine scrubber.
  • an additional benefit of the two-stage direct air capture configuration described herein is that issues related to amine degradation in the presence of oxygen are reduced or minimized.
  • process cycles using amine- based sorbents are constrained by the potential for degradation of amine sorbents when exposed to O2 at sufficiently high temperatures. While the amount of degradation varies depending on O2 concentration and temperature, noticeable degradation can potentially start to occur at temperatures as low as 70°C and/or at oxygen concentrations as low as roughly 1 - 2 vol%.
  • one option for organizing the sorbent material used for initial sorbent stage is to have an array of contactors with duct work to allow for rotation of which contactor(s) are in fluid communication with the working fluid loop / second separation stage at any given time. Gas flow into and out of each contactor is controlled by valves, such as valves mounted on each contactor.
  • each contactor can provide a sorbent environment that contains one or more monoliths.
  • An example of this type of configuration can be to use one or more skids that each support a (large) plurality of contactors. During operation, different adsorption beds are operating at different steps of a process cycle.
  • FIG. 5 provides a representation of this type of configuration.
  • a large array of contactors is represented.
  • FIG. 5 shows an array containing 64 contactors, it is understood that any convenient number of contactors can be used as sorbents for the initial separation stage, such as up to hundreds or even thousands.
  • the majority of the contactors 510 correspond to contactors performing a sorption step.
  • the remaining three contactors 520 are in some part of the regeneration process, such as desorption or cooling.
  • each contactor is a separate enclosure. This can allow the desorption and/or cooling steps of the initial separation stage to be performed at pressures greater than roughly 110 kPa-a. Performing the desorption and/or cooling steps at higher pressures can allow the initial stage effluent to be generated at a pressure above 110 kPa-a. Increasing the pressure of the initial stage effluent (which eventually becomes the input flow for the second separation stage) can potentially provide a variety of advantages for the second separation stage.
  • increasing the pressure of the input flow to the second separation stage provides a corresponding increase in the partial pressure of CO2 within the input flow. This can provide increased energy efficiency and/or reduced equipment footprint for the second separation stage apparatus.
  • An alternative to skid based processes are rotating wheels with sorbent beds composed of one or more monoliths.
  • rotating wheels When using a rotating wheel, different portions of the sorbent bed are simultaneously in the sorption, desorption, and cooling steps of the sorption / desorption cycle. The timing for each of these steps is equivalent to defining the fraction of the wheel which is exposed to the gas flows for that step.
  • gas channels rotate between the various process steps, hence simulating the operation of a multi-bed skid, but with a single contactor in a continuous process.
  • a benefit of rotating wheels is that the number of valves and length of piping are minimized, which in turn minimizes the pressure drop and resulting compression requirements. Further, rotating wheels result in more efficient use of plot space than skid based designs.
  • FIG. 6 illustrates an example of the partitioning for a rotary sorbent wheel for an initial separation stage process, such as the process illustrated in FIG. 2.
  • Area 610 of the wheel represents the section of the wheel which is being fed air 615 (i.e., the adsorption step).
  • Area 620 corresponds to the desorption step, which is performed while exposing area 620 to hot working fluid 625 for desorption.
  • Area 630 corresponds to the cooling step, where area 630 is exposed to cool working fluid 635. Additionally, a small sliver of the bed (not shown) is in the displacement step.
  • the displacement step section is an optional additional step that lies between the adsorption step 610 and desorption step 620 sections on the rotary wheel.
  • any air remaining in the volume of the sorbent bed after the adsorption step is displaced with a nitrogenrich gas, such as working fluid or a high purity nitrogen steam.
  • a nitrogenrich gas such as working fluid or a high purity nitrogen steam.
  • the volume of nitrogen can correspond to as little as the volume of the portion of the bed that is in the desorption step.
  • the displaced gas generated during this step is released to the atmosphere, but it is understood that some of the nitrogen-rich gas may exit from the system as part of the displacement purge.
  • the displacement step minimizes oxygen build up in the recycle gas.
  • FIG. 7 shows an example of how a pair of rotating wheel sorbent beds can be coupled to allow the rotating wheel beds to be integrated with a configuration where a working fluid is used during desorption and cooling, such as the configuration shown in FIG. 2.
  • rotary wheels 780 and 790 are shown. The wheels rotate in opposite directions. This can allow the cooling step 783 of wheel 780 to be aligned with the desorption step 792 of wheel 790, while the cooling step 793 of wheel 790 is aligned with the desorption step 782 of wheel 780.
  • the arrows represent the direction of gas flow for working fluid 738 and working fluid 739.
  • Working fluid 739 is used for cooling step 783 of the wheel 780.
  • the partially heated working fluid 739 is then passed through a heater 750 which heats the working fluid 739 to the desorption temperature.
  • the heat working fluid 739 is then fed to desorption step 792 on wheel 790.
  • working fluid 738 passes through cooling step 793 of wheel 790, heater 750, and then desorption step 782 on wheel 780. It is noted that separate heaters (not shown) could be used for working fluid 738 and 739, as opposed to having a single heater 750.
  • Example 1 Process Simulations at Ambient Pressure
  • Processes corresponding to the first or initial separation stage of configurations similar to FIG. 2 were modelled in a customized process modelling suite, based on the commercially available gPROMS program, that incorporates mass, energy and momentum balances in combination with adsorption physics to model cyclic gas adsorption processes.
  • the model was used to provide detailed representations of a single monolith unit cell, such as the cell shown in FIG. 4. Based on the ability to model individual cells, the simulations could be used to provide representative results for a target scale of operation.
  • the initial separation stage process is applicable to a variety of solid amine adsorbents.
  • alkylamine-appended MOF adsorbent mmen-Mg2(dobpdc) was used, “mmen” corresponds to N,N” -dimethyl ethylene diamine, while “dobpdc” corresponds to 4,4’- dioxidobiphenyl-3,3’-dicarboxylate.
  • MOF 4’- dioxidobiphenyl-3,3’-dicarboxylate.
  • the CO? adsorption isotherms for this material were taken from a journal article by Sinha et al (Ind. Eng. Chem. Res. 2017, 56, 750-764). Based on these published isotherms, model representations of the adsorption versus the partial pressure of CO2 are shown in FIG. 8 for various temperatures.
  • the MOF exhibits a step isotherm.
  • the MOF For partial pressures below the step (Pco2 ⁇ Pstep) the MOF has very little capacity for CO2, while at higher pressures (Pco2 > Pstep) the MOF has a very high capacity.
  • This on / off switch for adsorption comes with both benefits and challenges.
  • a benefit of a step isotherm is that the adsorbent material can be substantially fully regenerated. However, this also leads to a challenge due to the fact that desorption is all or nothing. For this reason step isotherms can be more challenging to use in processes based on pressure swing desorption.
  • heat is being delivered by the nitrogen rich recycle gas (e.g., the working fluid).
  • the recycle gas plays two roles, as the recycle gas both delivers the heat to the monolith as well as providing a partial pressure purge to sweep out desorbed CO2. Based on FIG. 8, a desorption temperature of 150°C would be needed in the absence of a purge gas.
  • the last temperature input for the process cycle is the temperature of the recycle gas leaving the second separation stage.
  • the temperature of the recycle gas leaving the second separation stage was set as 40 °C, which would be consistent with the second separation stage being an amine scrubber.
  • the lean recycle gas corresponding to 235 or 272 in FIG. 2, has a molar flowrate which is 3.1% of the air fed into the first separation stage concentrator process. This flowrate was obtained by optimizing the flowrate such that the adsorbent was sufficiently regenerated during the desorption step.
  • the flowrate of 235 / 272 is inversely related to the composition of CO2 in stream 265. For this case stream 265 has a CO2 mole fraction of 1 .1 %. This is the gas concentration being fed to the second separation stage. It is desirable to increase the concentration of stream 265 further. This would allow for a lower flowrate of recycle gas, as well as increase the efficiency of the second separation stage process.
  • the recycle gas flowrate will depend on the identity of the adsorbent material.
  • the effluent from the adsorption step is labeled decarbonized air.
  • the process removes 75% of the CO2 resulting in a decarbonized air CO2 mole fraction of 100 ppm.
  • the air is heated by 0.9°C as it passes through the bed on adsorption. This slight heating is a result of heat being transferred from the monolith (which is initially at 47 °C) to the gas, and not an effect due to the enthalpy of adsorption.
  • stream 235 / 272 When stream 235 / 272 is used to cool the sorbent bed 224, which is hot from the desorption step, it is preheated from 40°C to 72°C (245) prior to being heated (250) to 120°C (255) .
  • This heat integration allows for a more energy efficient process without the need to add large capital cost heat exchangers to the process.
  • a blower In addition to heating duty, a blower must be used to blow air through the beds in the adsorption step, as well as transport the recycle gas through the loop and wheels. The pressure drop through the wheels is very low and was calculated to be 0.34 kPa. In total this yields a blower requirement of 0.8 GJ / ton CO2.
  • the last step to consider is the displacement step. Before a gas channel enters into desorption, it contains air left in the gas channels from the adsorption step. If we were to immediately go to desorption by flowing hot recycle gas, the O2 in the gas channel would enter recycle loop. To minimize amine degradation it is required to have low O2 in the recycle loop. In the displacement step this air in the gas channel is displaced by a N2 gas. In the current calculations we assumed pure N2, however some small amount O2 may be acceptable. The displaced gas is then released to the atmosphere. This step likely represents the majority of N2 losses from the loop. The N2 flowrate of the displacement step totals to 1.8 moles N2 per mole of captured CO2.
  • Table 2 summarizes the stage 1 energy requirements.
  • the total stage 1 energy requirement is 3.9 GJ / ton CO2.
  • the volume of gas in the working fluid loop (used in initial stage desorption and cooling steps) was roughly 3 vol% of the volume of air exposed to the initial stage contactor during the sorption step. This resulted in CO2 partial pressures for the initial stage effluent of roughly 1.0 kPa to 1.5 kPa. Similar CO2 partial pressures in the initial stage effluent were obtained when modeling other types of sorbents as well, such as polyethylene imine, other types of MOF-based amine sorbents, and amine gels.
  • One option for increasing the partial pressure of CO2 in the initial stage effluent is to reduce the volume of working fluid by reducing the amount of nitrogen-rich recycle gas that is included in the working fluid.
  • the volume of nitrogen-rich recycle gas is constrained by the need to perform both heating and desorption during the desorption step.
  • Another option for achieving a higher partial pressure of CO2 is to pressurize the initial stage effluent.
  • the temperature of gas flow 272 (nitrogen-rich recycle stream from the second separation stage), which becomes working fluid 235, was set at 40°C.
  • the temperature of the heated working fluid 255 (heated by heater 250) was set 120°C.
  • the temperature of heated desorption output flow 381 (heated by heater 359) was set at 140°C.
  • the pressure in the working fluid loop was set at roughly 101 kPa-a, 200 kPa-a, or 400 kPa-a.
  • Table 3 shows the resulting CO2 partial pressure associated with the working fluid loop, as well as the energy costs required to achieve the target pressure in the working fluid loop.
  • the volume ratio of the volume of gas in the working fluid loop versus volume of air exposed to the sorbent bed in the initial adsorption step is also shown.
  • Table 4 and Table 5 provide additional details from the process simulations related to the composition of the various gas flows.
  • the gas flows are identified in part based on the corresponding reference numeral from FIG. 3.
  • adding the additional pre-heating step used in FIG. 3 allowed for a substantial increase in the mole percentage of CO2 in input flow for the second separation stage.
  • the flow 385 exiting from the pre-heating step has a CO2 concentration of 2.4 mol%, while the flow 265 exiting from the desorption step in Example 1 had a CO2 concentration of 1.1 mol%.
  • simply adding the pre-heating step resulted in a substantial increase in CO2 concentration to the second separation stage without performing any additional pressurization.
  • Embodiment 1 A method for separation of CO2 from an input flow stream, comprising: exposing a first gas flow comprising 600 vppm or less of CO2 to at least one first contactor of a plurality of contactors to form a first CCh-depleted gas flow, the at least one first contactor comprising a first sorbent having selectivity for CO2 sorption supported on one or more first monoliths, the exposing the first gas flow further forming a first sorbent comprising sorbed CO2; exposing a second gas flow comprising 600 vppm or less of CO2 to at least one second contactor of the plurality of contactors to form a second CCh-depleted gas flow, the at least one second contactor comprising a sorbent having selectivity for CO2 sorption supported on one or more monoliths, the exposing the second gas flow further forming a second sorbent comprising sorbed CO2; exposing the first sorbent comprising sorbed CO2 to a first heated working fluid
  • Embodiment 2 The method of Embodiment 1, wherein exposing the heated first sorbent to a first nitrogen-enriched gas comprising 95 vol% of N2 further comprises exposing the heated first sorbent to a recycled portion of the first partially heated working fluid, the recycled portion of the first partially heated working fluid optionally being cooled prior to exposing the recycled portion of the first partially heated working fluid to the heated first sorbent.
  • Embodiment 3 The method of any of the above embodiments, wherein the first output flow comprises 0.08 vol% or more of CO2, or wherein the second output flow comprises 0.08 vol% or more of CO2, or wherein the first nitrogen-enriched gas comprises 0.08 vol% or more of CO2, or wherein the second nitrogen-enriched gas comprises 0.08 vol% or more of CO2, or a combination of two or more thereof, or three or more thereof.
  • Embodiment 4 The method of any of the above embodiments, wherein the volumetric flow rate of the first CCb-containing working fluid is 5.0% or less of the volumetric flow rate of the first gas flow, or wherein the volumetric flow rate of the second CCb-containing working fluid is 5.0% or less of the volumetric flow rate of the second gas flow.
  • Embodiment 5 The method of any of the above embodiments, further comprising: exposing the first sorbent comprising sorbed CO2 to a pre-heating flow comprising 1.0 vol% or more of CO2 and 95 vol% or more of N2, the exposing the first sorbent comprising sorbed CO2 to a pre-heating flow being performed prior to exposing the first sorbent comprising sorbed CO2 to the heated working fluid; heating at least a portion of the first CCb-containing working fluid; exposing a third gas flow comprising 600 vppm or less of CO2 to at least one third contactor of a plurality of contactors to form a third CCb-depleted gas flow, the at least one third contactor comprising a third sorbent having selectivity for CO2 sorption supported on one or more third monoliths, the exposing the third gas flow further forming a third sorbent comprising sorbed CO2; exposing the third sorbent comprising sorbed CO2 to a third pre
  • Embodiment 6 The method of any of the above embodiments , wherein the exposing the first sorbent comprising sorbed CO2 to a first heated working fluid comprises exposing the first sorbent comprising sorbed CO2 to the first heated working fluid at a pressure of 150 kPa-a or more.
  • the first heated working fluid comprises a temperature of 100°C to 170°C
  • the second heated working fluid comprises a temperature of 100°C to 170°C, or a combination thereof
  • the first nitrogen-enriched gas comprises a temperature of 20°C to 80°C
  • the second nitrogen- enriched gas comprises a temperature of 20°C to 80°C, or a combination of two or more thereof, or a combination of three or more thereof.
  • Embodiment 8 The method of any of the above embodiments, wherein separating the first CC -containing working fluid comprises separating the first CCh-containing working fluid using an amine scrubber; or wherein separating the first CCb-containing working fluid comprises performing a temperature swing separation using a sorbent supported on a solid support; or wherein separating the first CCb-containing working fluid comprises performing a temperature swing vacuum-assisted separation using a sorbent supported on a solid support; or a combination thereof.
  • Embodiment 9 The method of any of the above embodiments, wherein the first sorbent comprises an amine-based sorbent, or wherein the second sorbent comprises an amine-based sorbent, or a combination thereof.
  • Embodiment 10 The method of any of the above embodiments, further comprising exposing the first sorbent comprising sorbed CO2 to a purge flow prior to exposing the first sorbent comprising sorbed CO2 to the first heated working fluid.
  • Embodiment 11 The method of any of the above embodiments, wherein the method further comprises: exposing a fourth gas flow comprising 600 vppm or less of CO2 to at least one fourth contactor of a plurality of contactors to form a first CCb-depleted gas flow, the at least one fourth contactor comprising a fourth sorbent having selectivity for CO2 sorption supported on one or more fourth monoliths, the exposing the fourth gas flow further forming a fourth sorbent comprising sorbed CO2; exposing the fourth sorbent comprising sorbed CO2 to a fourth heated working fluid to form a heated fourth sorbent and a fourth CCh-containing working fluid, the fourth CCb-containing working fluid formed by desorbing at least a portion of the sorbed CO2 from the fourth sorbent comprising sorbed CO2; exposing the heated fourth sorbent to a fourth nitrogen- enriched gas comprising 95 vol% of N2 or more to cool the heated fourth sorbent and to heat the fourth nitrogen
  • Embodiment 12 A system for separation of CO2, comprising: a plurality of initial stage contactors comprising a sorbent having selectivity for sorption of CO2, each initial stage contactor comprising a sorption step inlet, a sorption step outlet, at least one additional inlet, and at least one additional outlet, the plurality of initial stage contactors comprising at least a first initial stage contactor and a final initial stage contactor; a second separation stage comprising a second separation stage inlet, a product outlet, and a recycle outlet; an initial stage effluent conduit providing fluid communication between the second separation stage inlet and the at least one additional outlet of the final initial stage contactor, the initial stage effluent conduit containing an effluent flow comprising 95 vol% or more of N2 and 1.0 vol% or more of CO2; a recycle conduit providing fluid communication between the recycle outlet and the at least one additional inlet of the first initial stage contactor, the recycle conduit containing a recycle gas comprising 95 vol% or more of N2 and 0.08
  • Embodiment 13 The system of Embodiment 12, wherein the second initial stage contactor is the final initial stage contactor, and wherein the first initial stage contactor, the working fluid conduit, the final initial stage contactor, the initial stage effluent conduit, the second separation stage, and the recycle conduit comprise a working fluid loop.
  • Embodiment 14 The system of Embodiment 12, further comprising an intermediate conduit providing fluid communication between the at least one additional outlet of the second initial stage contactor and the at least one additional inlet of the final initial stage contactor, the intermediate conduit containing an intermediate fluid comprising 95 vol% or more of N2 and 1.0 vol% or more of CO2, the intermediate conduit further comprising an intermediate heater, an intermediate heat exchanger, or a combination thereof.
  • Embodiment 15 The system of Embodiment 14, wherein the first initial stage contactor, the working fluid conduit, the second initial stage contactor, the intermediate conduit, the final initial stage contactor, the initial stage effluent conduit, the second separation stage, and the recycle conduit comprise a working fluid loop.
  • Additional Embodiment A The method of any of Embodiments 1 to 11, wherein the at least one first contactor comprises at least one rotary sorbent wheel.
  • Embodiment B The system of claim 14 or 15, wherein the initial stage effluent comprises 2.0 vol% or more of CO2.
  • Certain features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges from any lower limit to any upper limit are contemplated unless otherwise indicated. Certain lower limits, upper limits and ranges appear in one or more claims below. All numerical values take into account experimental error and variations that would be expected by a person having ordinary skill in the art. [0101] The foregoing description of the disclosure illustrates and describes the present methodologies.

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  • Analytical Chemistry (AREA)
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  • Chemical Kinetics & Catalysis (AREA)
  • Separation Of Gases By Adsorption (AREA)

Abstract

L'invention concerne des systèmes et des procédés d'utilisation d'un procédé de capture à plusieurs étages pour la capture de CO2 provenant de l'air. Un premier processus de sorption ou de sorption initial est utilisé pour sorber le CO2 provenant de l'air. Après l'achèvement de la sorption de l'air, l'étape de désorption de l'étage initial est utilisée pour former un flux contenant du CO2 secondaire qui est passé dans un ou plusieurs étages de sorption supplémentaires. Ce flux contenant du CO2 secondaire peut être à une concentration d'environ 1,0 % en volume ou plus. La sorption de CO2 à partir du flux contenant du CO2 secondaire est mise en œuvre au moyen d'un procédé de mise en contact différent, tel qu'un procédé de mise en contact qui est plus efficace. Le second ou le dernier étage de sorption de CO2 peut produire un flux de sortie contenant du CO2 avec une concentration de CO2 de 80 % en volume ou plus, ou 90 % en volume ou plus, ou 95 % en volume ou plus. Ce flux de sortie de haute pureté peut ensuite être séquestré et/ou utilisé pour un traitement ultérieur.
PCT/US2023/079045 2022-11-14 2023-11-08 Capture directe à plusieurs étages de co2 provenant de l'air WO2024107569A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005103378A (ja) * 2003-09-29 2005-04-21 Seibu Giken Co Ltd ガス濃縮装置
US20090320679A1 (en) * 2008-06-27 2009-12-31 Praxair Technology, Inc. Methods and systems for helium recovery
US20140175336A1 (en) * 2012-12-20 2014-06-26 Exxonmobil Research And Engineering Company Co2 capture processes using rotary wheel configurations
WO2017053062A1 (fr) * 2015-09-25 2017-03-30 Exxonmobil Research And Engineering Company Adsorbant à deux étages et cycle de traitement pour separations de fluides
US20170113184A1 (en) 2010-04-30 2017-04-27 Peter Eisenberger System and Method for Carbon Dioxide Capture and Sequestration

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US20090320679A1 (en) * 2008-06-27 2009-12-31 Praxair Technology, Inc. Methods and systems for helium recovery
US20170113184A1 (en) 2010-04-30 2017-04-27 Peter Eisenberger System and Method for Carbon Dioxide Capture and Sequestration
US20140175336A1 (en) * 2012-12-20 2014-06-26 Exxonmobil Research And Engineering Company Co2 capture processes using rotary wheel configurations
WO2017053062A1 (fr) * 2015-09-25 2017-03-30 Exxonmobil Research And Engineering Company Adsorbant à deux étages et cycle de traitement pour separations de fluides

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SINHA ET AL.: "System design and economic analysis of direct air capture of CO through temperature vacuum swing adsorption using MIL-101(CR)-PEI-800 and mmen-Mg (dobpdc) MOF adsorbents", IND. ENG. CHEM. RES., vol. 56, 2017, pages 750 - 764

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